A computer graphics system for block diagram problems

This paper has described the design of an experimental system intended for solving complex problems. Facilities are provided for stating a problem as a labeled block diagram of arbitrary complexity. A block diagram can be drawn on a representative sheet that is many times larger than the screen of the cathode-ray tube. The block diagram may be structured into a hierarchy of sheets allowing blocks to be designed and specified by the user. The modeling subsystem provides a number of viewports so that more than one sheet can be displayed. To make entering of block diagrams easier, a drawing package that does not require commands for creating the diagram but uses only the operands to determine the command is a part of the system. Finally, a data structure in the host computer is provided to allow for easy access to data by any application program.